1. Field of the Invention
The present invention relates to a command apparatus in a gas laser oscillator. In particular, the present invention relates to a command apparatus in a gas laser oscillator, capable of commanding at high speed and with high precision.
2. Description of the Related Art
Conventionally, a gas laser oscillator is equipped with a plurality of laser power supplies according to required laser output. FIG. 3 illustrates an example of the gas laser oscillator in a related art, which is equipped with two laser power supplies. Gas laser oscillator 200 illustrated in FIG. 3 is equipped with two laser power supplies 110, 120. As illustrated in FIG. 3, commands generated in a CNC are transmitted to a communication IC 350 of an output command apparatus 100, and is separated into a bias command 410 and an output command 420.
These commands are applied D/A conversions by D/A converters 440a, 440b respectively, thereafter, added by an adder circuit 460. Subsequently, the added analog command voltage is commonly transmitted to each of laser power supplies 110, 120. The laser power supplies supply electric power, which is proportional to the analog command voltage, to electrodes 230, 240 of discharge tubes 210, 220 of the gas laser oscillator 200 through matching units 150, 160. According to these processes, the laser output from the gas laser oscillator 200 is controlled.
Generally, a certain bias command is always transmitted during a laser operational status, i.e., in a state where a laser beam can be output. The laser output from the gas laser oscillator 200 is controlled by changing the output command which should be added to the bias command.
The bias commands and the output command have a common value with respect to both of the laser power supplies 110, 120. In this connection, there are variations in characteristics of the electrodes 230, 240 of the discharge tubes 210, 220 in a laser gas circulation pass 250 of the gas laser oscillator 200, pressure of the laser gas in the discharge tubes 210, 220, auxiliary electrodes 310, 320 which are arranged adjacent to the electrodes 230, 240 respectively, and the matching units 150, 160. Hereinafter, these may be collectively referred to as loads of the laser power supplies.
To address the variations, in the related art, the command voltage adjustment circuits 130, 140 are provided in the laser power supplies 110, 120 respectively. These command voltage adjustment circuits 130, 140 adjusts the base discharge at the time of commanding the bias command, and adjusts the maximum injection power of the laser power supply at the time of commanding the maximum output command in each of the laser power supplies 110, 120, thereby absorbing the above-mentioned variations.
When adjusting the base discharge, only the bias command 410 is transmitted while the output command 420 is made into zero. It is visually checked by an operator that the laser oscillator 200 is in a state under a threshold value for oscillation (a laser output is 0 W), electric discharge by the discharge tubes 230, 240 being disappeared in the state, and auxiliary discharge by the auxiliary electrodes 310, 320 is maintained. Then, the operator adjusts variable resistors for offset adjustment (not illustrated) which are provided in the command voltage adjustment circuits 130, 140, respectively.
Moreover, when adjusting the maximum injection power of the laser power supplies, the bias command 410 and the maximum output command 420 are transmitted. In other words, the analog command voltage, in which the bias command and the maximum output command are added, is transmitted to the laser power supplies. The operator adjusts the variable resistors for gain adjustment (not illustrated) which are provided in the command voltage adjustment circuits 130, 140 respectively, while measuring the injection power of the laser power supplies so that the capability of the laser power supplies can be used maximally.
The number of the laser power supplies, which is provided in one oscillator, increases, as the gas laser oscillator 200 has higher output. Therefore, if the number of laser power supplies increases, it would be more complicated such that the operator would have to adjust the variable resistors of the command voltage adjustment circuits to adjust the base discharge and the maximum injection power.
In a command system disclosed in Japanese Registered Patent No. 4141562, in order to absorb the variations in the load of each laser power supply, DC current is detected to adjust the command voltage. The Japanese Registered Patent No. 4141562 requires the adjustment circuits 130, 140 in which the same analog voltage are used.
Furthermore, Japanese Registered Patent No. 2633288 discloses a laser oscillator which has an apparatus transmitting two kinds of commands, the bias command and an output command, to laser power supplies from a CNC. This system transmits the bias command and the output command independently from the CNC to each laser power supply, to adjust base discharge and maximum injection power.
However, according to Japanese Registered Patent No. 4141562, there are problems of a reduction of adjustment accuracy and a delay of response time for detection, due to variations in the command voltage adjustment circuits 130, 140 and the loads mentioned above and a change in environment such as temperature. Furthermore, there is a problem that the circuit configurations of the command voltage adjustment circuits 130, 140 are complicated. Further, the analog voltage adjustment circuit cannot manage the amounts of adjustment by the variable resistors for the offset adjustment and the gain adjustment of each laser power supply, with respect to the bias command and the output command which are same values in the plurality of power supplies. Thus, it is necessary to adjust the base discharge and the maximum injection power whenever any of the laser power supplies is broken down and is replaced.
Moreover, in Japanese Registered Patent No. 4141562, a processing defect may occur by an adjustment mistake of the base discharge. In other words, even in a state where only the bias command is transmitted and the output command is made to zero, a laser output may occur by exceeding a threshold value for oscillation of the laser oscillator. In such a case, there is a problem that a marking-off line is formed in a workpiece.
Furthermore, in Japanese Registered Patent No. 4141562, if the output command is caused to rapidly increase in a state where auxiliary discharge has disappeared, the laser power supply may be damaged due to an impedance missmatch of the laser power supply and the load. Moreover, when adjusting the maximum injection power, there are problems that a processing defect may occur due to insufficient injection power (a laser output is insufficient), and that the laser power supply, the matching unit and the discharge tube and the like are damaged due to excess injection electric power.
In Japanese Registered Patent No. 2633288, there is a problem that the number of data items to be transmitted increases (12 bit×two types×the number of the laser power supplies to be provided), if the number of the laser power supplies provided in one laser oscillator increases. Generally, the number of data items which is available is restricted according to a hardware (the communication IC) and the software in the CNC. Therefore, the number of laser power supplies is also defined according thereto. Moreover, this system, as illustrated in the flowchart of FIG. 3 (b) in Japanese Registered Patent No. 2633288, adjusts the base discharge and the maximum injection power for each of the laser power supplies in order. Accordingly, in cases where there are large number of laser power supplies, the adjustment time of the laser power supplies may be long significantly.
The present invention is made in view of such circumstances and, an object of the present invention is to provide a command apparatus in a gas laser oscillator capable of easily adjusting base discharge and maximum injection power, without lengthening adjustment time of laser power supplies even if there are large number of laser power supplies.